Took Plan B 5/24 and got my period on 5/27 could I still be pregnant?

I had unprotected sex with my partner and it was kinda a spur of the moment kind of thing so the following day I took Plan B just to be safe. I am now on my period and it's worse than ever. My cramps are so bad they are keeping me up at night which has never happened before. But my main concern is could I still be pregnant?